Digital piano won't power ON

[Alektron]

I found IP1 and CN3 (old CN2 from the old schematic), on the new schematic it's CN3. I included the location where these components reside on the Main Board (please see photo).

I also did a continuity test at IP1 (circuit protector) with my DMM. IP1 is doing fine. Next I checked the +5D voltage at IP1 to see if I can get this 5 Volt, but unfortunately I was only getting 650 mV , the same reading like at Diode #24.

I would like to ask anyone who reads this post, to give me a feedback if you can see 6 pictures with this posting. (one is a schematic, thank you)

 

[bushtech]

Can see the pictures fine.
Nice clear photos, what are you using to take them? Apologies for slightly OT.

 

[Alektron]

Can see the pictures fine.
Nice clear photos, what are you using to take them? Apologies for slightly OT.

Thank you for your reply, I use a Canon Power Shot A560.

 

[Alektron]

Can see the pictures fine.
Nice clear photos, what are you using to take them? Apologies for slightly OT.

Thank You.

It's actually not the camera, but the lighting procedure that makes these pictures turn out good.

I use two separate reading lamps with LED light bulbs in them, equal to a 100W regular light bulb, since the Flash from the camera is very powerful at such close distances, it was making the critical areas very bright, or non-visible.

Also the light from a fixed flash hits the shinny surface of the board in a straight direction, making some of these pictures inadequate.

However, with two lamps you can change the angle of the "lights" the way it hits the shinny board.

So there goes my secret .

 

[Alektron]

Any other suggestions what should I check?

 

[Tha fios agaibh]

As 73's de Edd discussed, there are multiple points along that point that should have your +5. If any component along this path is shorted, it will bring down the voltage.
Start checking components along this same path for continuity to see if anything is shorted. (With power off)

Example: put the meters red lead on test point F and black lead to the other side of diode (anode) to see if its shorted.

 

[Alektron]

Thank you for your reply. I did check those points and components, none of them seems to be shorted. However, to fully check some of these components, they should probably be removed from the circuit.

 

[Bluejets]

Can you provide a link to the new drawing.
Just it is difficult to mentally join up lines on different sheets.
Cheers Jorgo

 

[Alektron]

Can you provide a link to the new drawing.
Just it is difficult to mentally join up lines on different sheets.
Cheers Jorgo

73's de Edd informed me that he's going to make a unitized schematic from the one that I've got, which was a scanned in, an upside down deal, pages all over, very poor quality pdf.

Hopefully we are going to see a clear schematic after 73's de Edd joins the puzzle pieces together. I hope he'll be back.

 

[Alektron]

I guess 73's de Edd left the town with my schematics , and it doesn't seem like he's coming back for some odd reasons.

Anyone else willing to help me?

 

[73's de Edd]

Sir Alektron . . . . .

Au contraire . . . . . .messr . . . . it's just that there is lots of conflicting info on those two unit schematics and the amassing and amending of that info.

With my using your two best board shots of max relevance, and the amended schema . . . . we now continue.

Reviewing . . . .

The power supply passage of the + and - 15VDC supplies to the main board seem to be fine.
There is one interlocked voltage feature between the two boards in the respect of the +15 from the power supply needing to feed a sub regulated reference voltage to pin 5 of the IC34B section comparator.
DC voltage meter across C72 electrolytic, and see how close to 5.1 VDC that you are reading.

When CN107 gets interconnected to the PS board the VCC at pins 13 and 14 plummets down to hundreds of millivolts.

Your testing of Q8 power switching transistor reveals no dead short from C to E.

The diode that creates the 5 VDC Dee supply is being the D23 Schottky and is marked up on the foil pattern side as a fine line YELLOW rectangle, with it being a flat pack surface mount.

There is a black on black situation where there is being a jet black stripe of adhesive holding the flat pack in place during factory flow soldering bath operations.
Confirm that the adhesive is just being a bit in excess and being sloppy looking and that the diode case has NOT been hot and cracked and pooched its case from an overload and the heat thereby being produced.

A deviavce . . .
Evaluating the replacement of the super cap and its marked fine YELLOW circles, you commented on the hardmess of the two solder joints.
I am thinking that this boards birth goes back before the manufacturing transition to lead free solder.
What solder are you using now ? 60/40 rosin cored or the lead free type. Looks like you didn't do a pre-prep of applying a microdrop of liquid rosin flux to the joints before soldering.
That, along with a touch of rosin core 60/40 fresh solder and a well tinned tiplet should have resulted in a very shiny joint (example D8) instead of the resultant mottled grey.

I need Q8 transistor removed from the board, using that same 3 solder ball technique and rapidly walking the soldering iron tiplet between the 3 balls until Q8 leads reach solder release time.
Then the unit needs DC voltage monitoring of a connected CN107 to its mate at the pins 12 and 13, powering up for ONLY the time that is required for a voltage to show up on the meter . . . then power down.

Thassssit . . . . .

RELEVANT REFERENCING . . . . .

73's de Edd
.....

 

[Alektron]

Monsieur 73's de Edd.

Je suis désolé, je vous demande pardon...

I would like to apologize for my impatience and for my assumption, I just didn't know what's going on, and I would like to thank you very much for your efforts in pursuing a successful outcome in the repair of this instrument.

"There is a black on black situation where there is being a jet black stripe of adhesive holding the flat pack in place during factory flow soldering bath operations.
Confirm that the adhesive is just being a bit in excess and being sloppy looking and that the diode case has NOT been hot and cracked and pooched its case from an overload and the heat thereby being produced."

Ok, I am going to remove the Main board today and I'll start with the inspection of Diode #23.

" I am thinking that this boards birth goes back before the manufacturing transition to lead free solder. "

Actually its birth is after the transition from lead to lead free solder. This information was passed on to me by a repairing tech who told me that due to the new EPA regulations, the new solder was harder and more prone to micro cracks, sometimes in the connection of the chip to the board, the solder could break and result in a no connection, which would impede the booting up of the unit. Prior to joining this forum I was told to try to re-solder the EPROM chip IC4 and IC6 because if there is no connection on one of these chips to the board, it can create our situation of not powering up. I just simply remelted (very quickly and carefully) the already existing solder on IC4 and IC6 ( I did not add any solder), but unfortunately, this didn't improve anything.

However, I did notice that the solder is a very hard type, and this was also confirmed by the repair tech, but unfortunately no further info was shared afterwards.

" What solder are you using now ? 60/40 rosin cored or the lead free type. Looks like you didn't do a pre-prep of applying a microdrop of liquid rosin flux to the joints before soldering.
That, along with a touch of rosin core 60/40 fresh solder and a well tinned tiplet should have resulted in a very shiny joint (example D8) instead of the resultant mottled grey. "

I am using a 60/40 rosin cored solder, I included a photo, plus I also use separate rosin as a flux. When I was doing the S. Cap, I did add rosin as to pre-prep the joints, not sure why it didn't turn out shiny, but that could also be the lack of my expertise in the art of soldering.

" I need Q8 transistor removed from the board, using that same 3 solder ball technique and rapidly walking the soldering iron tiplet between the 3 balls until Q8 leads reach solder release time.
Then the unit needs DC voltage monitoring of a connected CN107 to its mate at the pins 12 and 13, powering up for ONLY the time that is required for a voltage to show up on the meter . . . then power down."

Roger that, I will remove the MAIN board, then inspect Diode 23, and remove Q8.

Thank you Again

I'LL BE BAACK !

 

[Bluejets]

Just be careful reflowing solder on the ic's.
Mate of mine spent 3 days trying to resolder the legs of a chip on a PS2 during "mods".
Turned out the manufacturer was a wake -up to mod chips being fitted and they made the original chip with "spring-up" legs.
Rather difficult to resolder especially on the high density type.

 

[Alektron]

Just be careful reflowing solder on the ic's.
Mate of mine spent 3 days trying to resolder the legs of a chip on a PS2 during "mods".
Turned out the manufacturer was a wake -up to mod chips being fitted and they made the original chip with "spring-up" legs.
Rather difficult to resolder especially on the high density type.

I wasn't too happy about doing it, but I got a magnifying glass loupe from an old projector.

Trying to see things that are so small was one of my first problems; however, stabilizing the solder iron while being only couple of micrometers away from the next leg, now that was my second major concern.

Hopefully things turned out good, time will tell...

 

[Alektron]

Sir 73's de Edd, I'm reporting back to you on the number 23 Diode.

" There is a black on black situation where there is being a jet black stripe of adhesive holding the flat pack in place during factory flow soldering bath operations.
Confirm that the adhesive is just being a bit in excess and being sloppy looking and that the diode case has NOT been hot and cracked and pooched its case from an overload and the heat thereby being produced. "

So I removed the board and I inspected Diode #23. It is a sloppy looking soldering job, but I do not see any crack on the case, although you can tell from the pictures that the "black" adhesive underneath is being in excess, otherwise I do not see any anomaly with this component.

I included some photos for your (and anyone else's ) review. Please follow the rabbit hole... eeerr... I mean the photos ...

Next on my list is Q8, I'll get to that as soon as possible.

 

[Alektron]

I cannot wait for the moment when I'll see this beautiful colorful screen come to life. Remember we might take this for granted compared to today's computer monitors, but we are talking about the late 90's here ...

Back in those days computer monitors were so big you could destroy Planet Alderaan with them, while Technics was releasing digital pianos with sleek colorful monitors, just the right size for performing any necessary task with them. What a wonderful design...

 

[73's de Edd]

You are right on the diode . . .I just did not have resolution on the photos that I could find.
If you were to take your DVM, using it in its diode test mode, and check the Vf of this diode, it just might mate up close to the voltage that we are seeing at terminals 12 and 13.

Good thing that you showed the Help Mate solder.

I first checked to see that the stuff was not just being a repackage of some far east import.
But . . . NO . . .its just being New Old Stock from the US but being new enough to have the use of Zip codes on it.
Possibly you found at a thrift store or as a yard sale find?
As Victor was / is ? mainly an auto supply products company, this solder blend would lean towards soldering repair of pinhole leaks on a brass radiator.
The real kicker is that is a 40% Tin and 60% Lead blend.
I once was pissed with the absolutely poor flow performance of 50/50 solder that I found on sale, and had not noticed its blend.
I would totally be dissatisfied with even less of a tin content. This is also the solder wire gauge diameter of which I used in wiring to tube sockets and to terminal board turrets-strips back in the late 30-40-early 50's.

You would also be BETTER served if you would take out 1/4 of your solder paste and dissolve it with denatured alcohol, down to the like consistency, of thin pancake syrup.
Then store it in a small sealable glass container. ( Cleaned out small TESTORS airplane dope bottle, etc. )
A round toothpick is a good applicator.

Edd

 

[Tha fios agaibh]

What solder are you using? View attachment 39538

To clarify, You are using 40/60 solder which isn't ideal for electrical use.
You want to use 60/40 rosin core.
That's a 60% tin to 40% lead ratio.

 

[Alektron]

"I first checked to see that the stuff was not just being a repackage of some far east import.
But . . . NO . . .its just being New Old Stock from the US but being new enough to have the use of Zip codes on it."

Thank you for your information. I'm open to any suggestions on what type of solder I should buy. Point me in the right direction and please tell me what brand I should get, and I will. ( Ain't no Mickey Mousing around here )

" You would also be BETTER served if you would take out 1/4 of your solder paste and dissolve it with denatured alcohol, down to the like consistency, of thin pancake syrup.
Then store it in a small sealable glass container. ( Cleaned out small TESTORS airplane dope bottle, etc. )
A round toothpick is a good applicator."

OK, I'll do that, I've got some bottles hanging around my RC airplane hangar ... Talking about airplanes, here is one my sweethearts, a CAP 232, with an OS 40 FX nitro engine, with a pits muffler under the cowl.


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" You are right on the diode . . .I just did not have resolution on the photos that I could find.
If you were to take your DVM, using it in its diode test mode, and check the Vf of this diode, it just might mate up close to the voltage that we are seeing at terminals 12 and 13."

I checked Diode #23 with the DVM in diode test mode, unit powered OFF of course. In both ways (forward and reverse biased ) I'm getting 20 mV.

 

[Alektron]

Next, I'm going to remove transistor Q8, let's see how that's gonna go...